What happens when an account is over HD Allocation?

726.44 / 500.00 MB

I have an account with this reporting in the SiteWorx list on NodeWorx. I believe it is this high b/c they do not POP3 for their email and just use the webmail which is basically like doing IMAP.

Will they stop getting new emails? I haven’t had any complaints from them so I guess everything is still working. What is really being blocked by them being over their quota?